Joysticks are routinely used in variety of control applications and provide a convenient way for an operator to provide control inputs. For example, a joystick could be used to control a fighter airplane, with the forward and aft motion controlling the elevator and the left and right motion controlling the ailerons. Joysticks suitable for such applications are well known in the art.
In some instances, it is desirable to provide control switches on the joystick handle to permit an operator to perform other functions. For example, in a fighter airplane, a missile launching switch could be located on the joystick control handle. The fighter pilot could then conveniently launch a missile without having to remove his hand from the flight controls.
There are known joysticks that include control switches on the joystick handle. Those switches are generally active switches that permit current to flow through the switch when the switch is in a closed position and cut current flow when the switch is open. An example of such a switch is a single-pole, single-throw momentary switch. Although such active switches perform acceptably, they have several drawbacks. For example, wires must be physically attached to the active switch. Because the joystick pivots in response to operator control movements the wires are exposed to significant repetitive motion. That motion can cause the wires to become brittle or otherwise weaken the wire and shorten the life span of the switch. Another drawback of active switches is that they require relatively large amounts of current to control the on/off signal. It would be preferable to have a switch that required less power.
Various types of passive sensing is known in the art. For example, U.S. Pat. No. 4,825,157 (the '157 patent) discloses a hall-effect joystick control. The patent does not disclose a switch mounted on the joystick. The joystick disclosed in the '157 patent includes an actuator member having a magnetic core. Hall-effect devices sense the motion of the magnetic core and produce control signals corresponding to the movement. One significant drawback to hall effect sensors is that they must incorporate a permanent magnet which degrades over time. The hall-effect sensor is also sensitive to external magnetic fields and may produce erroneous signals when exposed to an external magnetic field. Also, hall effect sensors are susceptible to shock and vibration damage, which makes them unsuitable in environments where shock and vibration are prevalent.